The invention relates to a disk drive with spindle motor and electrical connection arrangement according to the introductory part of claim 1. Such spindle motors are used for driving storage disks in hard disk drives.
The spindle motor for driving the storage disk(s), which is arranged on a baseplate of the disk drive and consists of armature and stator, has at least one bearing, fitted on a central shaft, by which the armature is mounted rotatably with respect to the stator. The stator consists of a laminated iron core, or stack, with coils wound on it, which will be called the xe2x80x9cwinding stackxe2x80x9d0 for short, and which is arranged on the baseplate by means of a xe2x80x9cwinding supportxe2x80x9d, with a concentric air-gap between the winding stack and a ring- shaped permanent magnet fitted inside the armature and preferably encased in an iron yoke. Sequential passage of current through the coils sets up rotating magnetic fields which, in co-operation with the, preferably radially aligned, pole pairs of the permanent magnet, generate the torque required to drive the armature.
The difficulty that arises where disk drives with spindle motors are used for driving storage disks is the electrical connection of the coils, located within the drive and therefore in the xe2x80x9csterile zonexe2x80x9d, to the printed circuit board, arranged outside the drive. This connection needs to be made easily, reliably, and at low cost. Furthermore, electrical connection to the printed circuit board needs to be done as easily and quickly as possible, while the baseplate leadthrough must be hermetically sealed.
DE 19748150 has disclosed a spindle motor with a connection of the abovementioned kind which permits quick and easy connection and allows the winding stack to be injection-moulded outside the base flange and before electrical connection takes place, whilst affording the requisite insulation and sealing of the electrical connection area.
This is achieved by providing contact pins in or on the winding support, one free end of the pins being formed as a soldering terminal to which the wire ends of the coils of the winding are connected. The other ends of the contact pins pass through an opening in the baseplate and, after the connector has been fitted, can be connected to the springy connection tags or contact springs by methods that are known in themselves.
One drawback of this form of construction is that several electrical connection-points are required: first, between the ends of the winding wires and the ends of the contact pins formed as soldering terminals; second, between the other free ends of the contact pins and the springy connection tags or contact springs; and third, between the springy connection tags or contact springs and the contact lands on the printed circuit board. The printed circuit board, which carries, among other things, the control electronics for driving the spindle motor, is mounted on the back of the baseplate. Whilst assembly of the winding stack into the baseplate is on the whole facilitated, the increase in production costs due to the additional contact pins required is a disadvantage.
A further drawback of this construction is that the increased number of contact-points increases the probability of a defect in this area. Moreover, cold solder joints due to imprecisely-defined and/or varying electrical contact resistance in the contact-points may lead to power losses and hence to variations in the rotational speed of the spindle motor, which may cause errors in the recording or reading of the data on the hard disk.
The problem tackled by the present invention is to develop a spindle motor with electrical connection of the type stated at the outset in a way which fully retains the advantages of DE 19748150, and
allows simpler and hence cheaper electrical connection in terms of design, production, assembly and maintenance, and
allows faster and more reliable connection in terms of mechanical and electrical malfunctions, and yet
still allows the winding stack to be injection-moulded before assembly in the baseplate, and still affords the required insulation and sealing of the baseplate leadthrough area.
In accordance with the invention this problem is solved by the technical teaching of claim 1.
The key feature of the invention is that at least one terminal tag arranged in or on the winding support is formed at one free end in the region of the coils as a soldering terminal for making a permanent electrical connection between the wires of the coils and the tag, and is formed at its other free end as a contact spring exerting the necessary contact force for good electrical contact to corresponding contact lands on a printed circuit board.
Here xe2x80x9csoldering terminalxe2x80x9d0 signifies that a mechanically stable electrical conductor is presented which is constituted of a suitable material, and has a suitable surface, for a sound soldered joint.
This yields the advantage that the wire ends of the coils of the winding stack can be connected to the terminal tags prior to the final assembly of the spindle motor. Furthermore, the winding stack bonded to its terminal tags can be completely injection-moulded without hampering or impairing the subsequent connecting to the printed circuit board.
A further advantage is that the connecting of the wire ends of the coils to the respective terminal tags can be fully mechanized. In a first step, the wire ends of the coils are wound round the tags by machine, and in a second step these contact-points can then be connected e.g. by machine soldering.
Another major advantage of the invention is that by incorporating the terminal tags into the winding support, on the one hand it is possible to dispense with the special connector serving as holder for the terminal tags, and on the other hand the contact pins used in the state of the art for connecting the coil wire ends of the winding to the contact springs are also no longer required.
The smaller number of components means that manufacturing and assembly costs are reduced, while time-consuming and cost-intensive hand soldering for making the electrical connections between contact pins and contact springs is eliminated.
This brings the further advantage that the risk of the occurrence of cold solder joints is considerably reduced.
In accordance with the present invention, the cross-section of the springy terminal tags or contact springs in or on the winding support is preferably rectangular at least in partial regions, which substantially determines the location of the electrical contact-points between the terminal tags and the control electronics, and prevents the tags from warping with respect to the winding support and/or the contact lands on the printed circuit board.
The terminal tags may be at least partly axially displaceable in or on on the winding support, the axial displacement being limited by the provision of an axial stop. This stop may be provided on the terminal tag e.g. in the form of a radial collar which abuts against the upper side of the winding support. The stop may be formed on the terminal tag for example by stamping or upsetting. In this case the terminal tag must be inserted through the winding support from above in the course of assembly.
Terminal tags with a rectangular cross-section extending over their entire length are preferred.
The terminal tags may extend through the winding support in the axial and/or radial direction, or, in another embodiment, be fixed to the outer shell of the winding support.
In a preferred embodiment, the terminal tags are arranged on the inside, i.e. in the region between winding stack and shaft.
Further advantageous features and embodiments of the invention are the subject-matter of the dependent claims.
The invention will now be described in detail with reference to several drawings illustrating ways of carrying out the invention. Further features and advantages of the invention will become apparent from the drawings and the description thereof.